Apparatus and method for preventing refrigerant condensing



3,126,713 EVENTING REFRIGERANT CONDENSING 6 Rm m,

6 R1 A11 d A m saw J March 31, 1964 APPARATUS AND METHOD FOR IN MULTIPLE COMPRESSOR ARRANGEMENTS wlrlfdprrllllflavtrlllll Ill INVENTOR: W

a, ATTORNEYS.

United States Patent This invention relates to a refrigeration system, and in general, to a refrigeration system having at least two compressors therein adapted to operate singly or in combination in accordance with load requirements sensed by a controller. More particularly, this invention relates to means comprising both method and apparatus for preventing refrigerant from condensing in the idle compressor of a multiple compressor refrigeration system.

In previous multiple compressor refrigeration systems having two or more compressors, a condenser, expansion means and an evaporator connected in refrigerant flow relationship, a multitude of problems have been encountered, arising from the different temperature levels which may be attained by the compressors in such systems. Each compressor is a large heat reservoir because of its size and may be subject to different ambient conditions as, for example, the temperature of the ambient air surrounding each compressor may be different and the air may fiow over one compressor to cause radiation therefrom and not over another. The refrigerant piping connecting the compressor may not provide sufficient heat transfer to equalize the temperature levels of the difierent compressors. Hence when one compressor is running and another is idle, the inoperative compressor may cool off sufiiciently to act as a condenser resulting in the accumulation of refrigerant liquid in the top of the cylinder. Subsequently, when the idle compressor is started, the accumulated refrigerant liquid creates severe slugging problems resulting in discharge valve damage and compressor failure.

Various attempts have been made to solve the problem of compressor failure in multiple compressor refrigeration systems, none of which has proven to be entirely successful. One proposal was to utilize a check valve in the discharge line of the second compressor in a two compressor refrigeration system. Though the collection of refrigerant liquid in the top of the cylinder of the second compressor was somewhat reduced, there continued to be a high rate of compressor failure. It has been determined that the check valve alone was unable to insure a complete valve seal, for if a sufficiently heavy loading spring were used to maintain the check valve seated then the compressor was required to pump against the force of the spring during operation, thus greatly reducing the efficiency of the compressor and increasing the motor power requirements. If a lighter spring were used fluttering occurred and refrigerant flow to the cylinder resulted, virtually as though no check valve were used. Because of these problems it has been proposd that separate refrigerant circuits be employed, each having its own compressor, such that when increased load capacity is required, more than one of the refrigerant circuits would be utilized. This is obviously a costly, complicated and undesirable approach.

An object of the present invention is to provide a multiple compressor refrigeration system wherein the disadvantages and deficiencies of prior systems are obviated.

Another object of the present invention is to provide a multiple compressor refrigeration system having novel means therein for preventing refrigerant liquid from accumulating in a cylinder of the idle compressor and subsequently causing compressor failure.

Still another object of the invention is to provide a refrigeration system having at least two compressors with means for preventing high pressure vaporous refrigerant from an operative compressor from entering a cylinder of the idle compressor and for bleeding pressure from the idle compressor to the suction line.

Another object of the present invention is to provide a refrigeration system having two compressors with combination check and bleed valve means for preventing refrigerant liquid accumulation in the cylinder of the idle compressor.

Yet another object of this invention is to provide a novel method of operating a multiple compressor refrigeration system.

These and other objects of the invention which will become hereinafter more apparent are obtained by providing a refrigeration system having at least two compressors, the second compressor being adapted to operate sequentially to provide additional load capacity as desired, with means for preventing refrigerant liquid condensation in the second compressor comprising check valve means in the discharge line of the second compressor and bleed means between the second compressor and check valve means therefor communicating with the suction line. When the second compressor is idle the check valve means prevent high pressure vaporous refrigerant from the first compressor from entering the cylinder of the second compressor. In the event that any high pressure vaporous refrigerant is trapped in the discharge line of the second compressor, the bleed means will vent such high pressure vaporous refrigerant to the suction line. Thus, by the present invention novel method and apparatus have been evolved for preventing refrigerant from condensing in the idle compressor in a multiple compressor refrigeration system.

This invention relates to a refrigeration system comprising a first compressor, a second compressor, a condenser, expansion means and an evaporator, discharge line means connecting said first compressor and said second compressor to said condenser, suction line means connecting said evaporator to said first compressor and to said second compressor, control means for energizing one compressor in response to a first condition and for energizing both compressors in response to a second condition and means for preventing refrigerant condensation in the second compressor comprising valve means disposed between the first and second compressors for preventing the passage of discharge gases from the operative compressor to the idle compressor and means for bleeding the discharge pressure between the idle compressor and the valve means to the suction line means.

This invention also relates to a method of operating a multiple compressor refrigeration system comprising a first compressor, a second compressor, discharge line means, a condenser, expansion means, an evaporator and suction line means interconnected in refrigerant flow relationship, said method comprising the steps of actuating the first compressor in response to a first load condition, preventing the flow of refrigerant from the first operative compressor to the second idle compressor and communicating the discharge side of the second compressor to the suction line means to prevent refrigerant liquid accumulation in the cylinder of the second compressor.

The specific structural details and their mode of func tioning will be made most manifest and particularly pointed out in clear, concise and exact terms in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a schematic diagram of a refrigeration system embodying the present invention;

FIGURE 2 is a schematic diagram of one form of the present invention comprising a check valve and bleed means including an automatically-actuated bleed valve;

FIGURE 3 is a schematic diagram of a second form of the present invention comprising a check valve and bleed means including a capillary tube;

FIGURE 4 is a cross-sectional view of a third form of the present invention comprising an integrally formed check and bleed valve mechanism, the check valve being shown in the open position and the bleed valve being shown in the closed position; and

FIGURE 5 is a cross-sectional view of the integrally formed check and bleed valve mechanism of FIGURE 4 illustrating the check valve in the closed position and the bleed valve in the open position.

Referring now more particularly to the drawings, like numerals in the various figures will be taken to designate like parts.

Considering FIGURE 1, there is indicated generally at 1th a refrigeration system comprising a first compressor and a second compressor. It will be understood that more than two compressors may be utilized in the refrigeration system of the present invention and further that each of the compressors may have more than one cylinder. Each of the compressors l2 and 14 discharges high pressure vaporous refrigerant into the discharge line means 15. Such discharge line means may comprise a line 16 connecting compressor 12 to the condenser 26 and the lines 18 and 19 connecting compressor 14 to the line 16. From the condenser 24 refrigerant flows through expansion means 21 which may be a conventional expansion valve or capillary tube, to the evaporator 22. From the evaporator 22 vaporous refrigerant flows through the suction line means 24 for return to compressors 12 and 14. The line 26 connects the evaporator 22 to the compressor 12 and the line 27 connects the suction line means to the compressor 14.

Provided in the discharge line 13, 19 of the second compressor :14 are the novel means of the present invention for preventing accumulation of liquid refrigerant in the cylinder of the compressor 14. The means 29 are disposed in the discharge lines 18 and 19 and are adapted to prevent the flow of high pressure vaporous refrigerant from line 16 through lines 18 and 19 to compressor 14 when the compressor 12 is operative and the compressor 14 is idle. The means 29 are adapted to bleed high pressure vaporous refrigerant from the discharge line 18 through the bypass line 36 to the suction line means 24.

A suitable controller 31 is provided to control the energization of the motors within the compressors 12 and 14 respectively. It will be understood that in response to a first load requirement, the compressor 12 will be energized and compressor 14 will remain idle. In response to a second load requirement, a demand for additional capacity, the second compressor 14 will be energized so that both compressors 12 and 14 are operative.

Referring now to FIGURE 2, there is shown schematically one form of the means 29. Provided between lines 18 and 19 is a suitable T 33 by means of which the bypass line 3% may be connected to the lines 18 and I). Disposed in the line 19 is a conventional one-way check valve 32, which prevents the how of refrigerant from line 16 through line 19 to line 18 and which permits the flow of refrigerant firom line 18 through line 19 into line 16. Provided in the bypass line 30 are valve means suitably actuated in response to a predetermined condition. Valve 34 may be electrically operated in response to the stopping and starting of the second compressor or the valve may be pneumatically actuated in response to suction pressure. In either event the valve 34 is open when the second compressor is stopped by controller 3}. and is closed when the second compressor is actuated by controller 31.

Referring now to FIGURE 3, there is illustrated another form of the means 29. Provided in the lines 13 and 19 is a T 37 which connects the lines 18 and 19 to one another and which connects the bypass line 36 to the lines 13 and 19. Disposed in the line 19 is a conventional oneway check valve 36, which functions in the same manner as check valve 32. Provided in the line 30 is a capillary tube 38. The rate of flow through the capillary tube is small with respect to the pumping rate of the second compressor but is large enough to assure reducing the pressure between the compressor discharge and the check valve to virtually suction pressure in a relatively short period of time, of perhaps 3 to 5 minutes.

Considering now FIGURES 4 and 5, there is shown a third form of the means 29. In this form of the invention the check valve and the bleed valve functions combined in a single unit. The valve body 41 comprises a cylindrical housing or casing 42 to which is adapted to be connected an inlet fitting and a pair of outlet fittings. The inlet fitting 43 is suitably secured in opening 44 in a wall of the casing 42. An outlet fitting 45 is suitably connected in opening 46 in the wall of casing 42. The outlet fitting 47 is secured to the support member 48, which is externally threaded and engages in the internally threaded bore 49 of insert member 50 which is connected in turn to the cylindrical hOusing 42. Movable within the bore 52 defined in the cylindrical casing 42 is a piston 51. Secured to the piston are valve means 53, which are adapted to engage valve seat 54 formed at the top of the insert member 50. The piston is biased downwardly by spring 56 which is disposed between the top of the piston 51 and the cap 55 which closes the end of the bore 52 in the cylindrical casing 42. The piston is moved upwardly to the position shown in FIG- URE 4- by the pressure of the high pressure vaporous refrigerant passing from the discharge line 18 through inlet fitting 43 to the outlet fitting 45 and discharge line 19.

Connected between the upper end of the support member 48 and a flange 50 on the generally cylindrical insert member 51') is a flange 57 on an end of spring retainer 58. Operatively connected between the flange 59 on the upper end of the spring retainer 53 and an annular flange 61 on the bleed valve 62 is a spring 60. As seen in FIGURE 4 the bleed valve 62 is adapted to close the outlet opening 63 in the support member 48.

Extending upwardly from the bleed valve 62 is an extended cam surface 64 which is adapted to be contacted by an actuating stem 65 depending downwardly from the piston 51.

O-ring seals 66 and 67 may be provided between the support member 48 and the insert member 59 and between the support member 48 and the outlet fitting 4-7, respectively, to prevent the passage of high pressure vaporous refrigerant from the bore 52 within housing 42.

FIGURE 5 is a cross sectional view of the combined check valve and bleed valve of FIGURE 4 illustrating the positions of the check valve and bleed valve when the compressor 14 is inoperative. The spring 56 overcomes the reduced pressure beneath piston 51 and urges the piston downwardly. As the piston 51 moves downwardly, the actuating stem 65 (on piston 51) bears against the extended cam surface 64 secured to the bleed valve 62, causing the bleed valve 62 to be displaced from the opening 63 in the support member 48, thus permitting the discharge of refrigerant from line 18 to the bypass line 30 and back to the suction line means 24.

Operation Considering the operation of the refrigeration system of FIGURE 1, it is apparent that the compressor 12 will be actuated in response to a first load condition sensed by controller 31. High pressure vaporous refrigerant will be discharged through the line 16 to the condenser 20. In the condenser, which may be either air-cooled or water-cooled, refrigerant will be condensed and the flow of the condensed liquid refrigerant from the condenser 20 to the evaporator 22 will be metered by the expansion means 21. In the evaporator 22 the refrigerant will vaporize and expand, withdrawing heat from the ambient surrounding the coils of the evaporator. The refrigerant vapor will return through the suction line means 24 to the compressor 12. It is to be understood that the means 29 will prevent refrigerant from passing through line 19 to line 18 to the cylinder of the idle compressor 14.

In response to a second load condition, the controller 31 will cause the compressor 14 to be actuated. Therefore, both compressors 12 and 14 are operative to forward high pressure vaporous refrigerant through the discharge line means 15 to the condenser 20.

In the event that the load requirement is reduced, the controller 31 will cause the compressor 14 to be deenergized. At this time, the check valve mechanism within the means 29 will close again, terminating the flow of high pressure vaporous refrigerant from line 1? through line 18 to the cylinder of compressor 14, and any of the high pressure vaporous refrigerant trapped in the line 18 will be bled through the bypass line 30 to the suction line means 24. In this manner the accumula tion of refrigerant in the cylinder of the compressor 14 is obviated and in subsequent start-up of the compressor there is little likelihood of liquid being slugged through the discharge valve of compressor 14 and damaging the valve so as to ultimately result in compressor failure.

The functioning of the means illustrated in FIGURE 2 is believed to be clear from the foregoing. The check valve 32 prevents the flow of high presure vaporous refrigerant through the line 19 to the line 18 when compressor 14 is idle and compressor 12 is operative. When both compressors are operative, refrigerant from compressor 14 passes through the line 18, means 29, and the line 19 to line 18. In the event that both compressors have been operative and the operation of compressor 14 is terminated, the valve 34, which is energized electrically in response to termination of the compressor or pneumatically in response to the suction pressure, will open to permit the bleeding of refrigerant from line 18 through line 30 to the suction line means 24.

The apparatus of FIGURE 3 functions in a similar manner to that disclosed in FIGURE 2 except that the capillary tube 38 provides a continuous bleed from the line 18 to the line 30. It will be understood that the flow rate throught he capillary tube 38 is small with respect to the pumping capacity of the second compressor 14. However, it is large enough to assure that pressure equalization will occur between the line 18 and the line 30 in a reasonable time (three to six minutes) when the compressor 14 is inoperative.

The operation of the combined check and bleed valve 29 illustrated in FIGURES 4 and 5 is believed to be evident from the description aforenoted. The piston 51 and valve means 53 function as a check valve and element 62 functions as a bleed valve. As shown in FIGURE 4, when the compressor 14 is operative high pressure forces the piston 51 upwardly permitting the flow of refrigerant from line 18 to line 19. The bleed valve 62 is biased by the spring 60' to close the opening 6 3, preventing the fiow of refrigerant to the bypass line 30*. As seen in FIGURE 5, when the operation of the compressor 14 has been terminated, the pressure below the piston 51 is reduced and the piston 51 is biased downwardly by spring 56 to terminate the passage of fluid between lines 18 and 19. Actuating stem 65 secured to the piston 51 engages the ex tended cam surface 64 on the bleed valve 62, causing the bleed valve 62 to be moved from engagement with the opening 63 and permitting the flow of refrigerant from line 18 to line 30 and back through the suction line means 24. In this way damage to the second compressor is prevented, for liquid accumulation in the cylinder thereof is virtually obviated. By the present invention there has been provided an expedient solution to the problem of staging two or more compressors in a unitary refrigeration system.

While I have described presently preferred embodiments of the invention, it will be understood that the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of operating a multiple compressor refrigeration system comprising a first reciprocating compressor, a second reciprocating compressor, discharge line means, a condenser, expansion means, an evaporator and suction line means interconnected in refrigerant flow relationship, said method comprising the steps of actuating the reciprocating compressors in response to a predetermined load condition, deenergizin-g one compressor in response to a reduced load condition, preventing the flow of refrigerant from the other operative compressor to said one idle compressor, and communicating the discharge side of said one idle compressor to the suction line means only when said idle compressor is stopped to prevent refrigerant liquid accumulation in the cylinder of said idle compressor.

2. In a refrigeration system, the combination of a first compressor, a second compressor, a condenser, expansion means, an evaporator, discharge line means connecting said first compressor and said second compressor to said condenser, suction line means connecting said evaporator to said first compressor and to said second compressor, control means for energizing said first compressor in response to a first condition and for energizing both compressors in response to a second condition, and means for preventing refrigerant condensation in said second compressor comprising valve means disposed between the first and second compressors for preventing the passage of dis charge gases from the operative compressor to the idle compressor and bleed means for releasing discharge pressure between the idle compressor and the valve means to the suction line means, said valve means comprising a one-way check valve and said bleed means comprising a valve in a line connecting the discharge line means and the suction line means.

3. The refrigeration system as in claim 2 wherein the valve in the line connecting the discharge line means and the suction line means is opened in response to stopping of the second compressor.

4. In a refrigeration system, the combination of a first compressor, a second compressor, a condenser, expansion means, an evaporator, discharge line means connecting said first compressor and said second compressor to said condenser, suction line means connecting said evaporator to said first compressor and to said second compressor, control means for energizing said first compressor in response to a first condition and for energizing both compressors in response to a second condition, and means for preventing refrigerant condensation in said second compressor comprising valve means disposed between the first and second compressors for preventing the passage of discharge gases from the operative compressor to the idle compressor and bleed means operable in response to stoppage of said second compressor for releasing discharge pressure between the idle second compressor and the valve means to the suction line means.

5. In a refrigeration system, the combination of a first compressor, a second compressor, a condenser, expansion means, an evaporator, discharge line means connecting said first compressor and said second compressor to said condenser, suction line means connecting said evaporator to said first compressor and to said second compressor, control means for energizing said first compressor in response to a first condition and for energizing both compressors in response to a second condition, and means for preventing refrigerant condensation in said second com- 10 pressor comprising valve means disposed between the first and second compressors for preventing the passage of discharge gases from the operative compressor to the idle compressor and bleed means for releasing discharge pressure between the idle compressor and the valve means to the suction line means, said valve means and said bleed means being integrally formed and comprising a combination check and bleed valve.

Buschmann Aug. 29, 1950 Algren May 30, 1961 

1. A METHOD OF OPERATING A MULTIPLE COMPRESSOR REFRIGERATION SYSTEM COMPRISING A FIRST RECIPROCATING COMPRESSOR, A SECOND RECIPROCATING COMPRESSOR, DISCHARGE LINE MEANS, A CONDENSER, EXPANSION MEANS, AN EVAPORATOR AND SUCTION LINE MEANS INTERCONNECTED IN REFRIGERANT FLOW RELATIONSHIP, SAID METHOD COMPRISING THE STEPS OF ACTUATING THE RECIPROCATING COMPRESSORS IN RESPONSE TO A PREDETERMINED LOAD CONDITION, DEENERGIZING ONE COMPRESSOR IN RESPONSE TO A REDUCED LOAD CONDITION, PREVENTING THE FLOW OF RE- 